1. Field of the Invention
The present invention relates to an improved access arrangement for pits designed for use in servicing aircraft at docking, loading and refueling terminals.
2. Description of the Prior Art
At modern aircraft terminals servicing of aircraft on the ground is frequently performed using prefabricated pits which are installed at aircraft docking, fueling and loading areas beneath the surface of the tarmac across which aircraft travel during docking and departure maneuvers. The pits are typically formed of fiberglass, steel or aluminum and are constructed as enclosures with surrounding walls, and an access lid at the top of the walls. The pits are installed below the surface of loading and refueling aprons at aircraft terminals, remote parking locations and maintenance bases.
The purpose of the pits is to allow ground support functions to be carried out from subsurface enclosures. These ground support functions include the provision of fuel, the provision of electricity to the aircraft while it is in the docking area, the provision of air for cooling the aircraft interior, the provision of pressurized air for starting the aircraft engines, and for other aircraft support activities on the ground. The use of subsurface pits eliminates the need for mobile trucks, carts and other vehicles which are otherwise present in the loading area and which interfere with the arrival and departure of aircraft in the vicinity of a loading gate. The use of subsurface pits also allows the provision of fuel, power, cooling and pressurized air, and other supplies from a central location. The necessary fluid supplies and electrical power can be generated or stored with great efficiency at a central location, as contrasted with mobile generating or supply vehicles.
The pits located below the aircraft terminal area house valves, junction boxes, cooling air terminations and other terminal equipment that is temporarily connected to an aircraft that has been docked. Umbilical pipes and lines, otherwise housed within the pits, are withdrawn from the pits through hatches therein and are coupled to a docked aircraft to supply it with fuel, air for cooling the aircraft interior, pressurized air for starting the engines, and electrical power.
The pits are constructed with hinged lids that are movable between open positions allowing access to the pits and closed positions which are flush with the surface of the docking, loading or refueling area across which aircraft travel and beneath which the pits are mounted. Because the pits are located beneath the surface upon which the aircraft travel while on the ground, aircraft servicing personnel must descend into the pit in order operate valves, withdraw aircraft refueling lines, electrical power lines, air conditioning ducts, and to otherwise utilize the pit for its intended purpose.
To enable aircraft servicing personnel to descend into an aircraft pit, an upright ladder is typically mounted on one of the pit walls. The ladder has a pair of upright side rails which are normally held in a vertical disposition out a few inches from the surface of the wall. Transverse, horizontal ladder rungs or steps extend between the side rails of the ladder. The space between the ladder rung and the wall upon which the ladder is mounted enables a person to achieve a foothold on the ladder rungs as the individual descends the ladder.
One significant difficulty which currently exists with subsurface aircraft servicing pits is that because the lid of the pit must shut flush with the paved surface across which the aircraft move while on the ground, it is not possible to provide hand holds or grips protruding above grade to assist aircraft servicing personnel in beginning a decent into the pit, or to assist such personnel in emerging from the pit. As a result, personnel who must gain access to the pit are forced to get down on their hands and knees in order to begin the descent. Even so, the initial steps down into the pit are still quite difficult to make, as the descending service personnel cannot gain a secure hand grip on the ladder while taking the first few steps from the top of the ladder down. The present practice of descending the ladder of a subsurface aircraft servicing pit is therefore somewhat unsafe. If a worker's foot slips on a ladder rung either at the beginning of the descent or in emerging from the pit, the worker can easily fall down into the pit. There has heretofore been no steady and accessible hand grip which can be utilized to prevent such a fall.